Dental articulators are used in conjunction with models or casting in developing prosthodontic dental appliances. In typical applications, a dentist will make an impression of the patients mouth and utilize this impression to cast a model. The model is then mounted on an articulator to insure that the cap, crowns, bridges or dentures are sized and shaped to correctly fit in alignment with the remaining piece in the patients mouth. Dental technicians initially fabricate the model and then mount the model on the dental articulator for final finishing and fitting steps.
It is necessary to support such models in a relatively natural hinge relationship so as to mimic as closely as possible the biting movements. If the prosthodontic appliances are not properly shaped, a patient will be forced to undergo multiple adjustments which could possibly damage his or her teeth. It should be noted that a natural bite involves many motions in addition to the up and down motion as the human jaw is capable of side to side and back and forth motions.
It is an important feature that a dental articulator permit the ready separation of the components of dental models while allowing for their realignment in proper registration. Thus it is necessary for dental technicians to perform detailed work on prosthodontic appliances mounted onto dental articulators which requires that the articulator permit model separation. Such model separation will improve the quality of the prosthodontic appliance as well as decrease the quantity of time taken for its production and the attenuate costs inherent therewith.
There is a wide variety of dental articulators and various degrees of sophistication presently available.
There have been many attempts for a number of years to solve the problem of accurately and inexpensively using an articulator for use with a dental model. Such articulator range from simple devices affording only fixed pivotal movement between a pair of casts to complex devices which simulate the full range of occlusal and masticatory registrations unique to the dental patient. General speaking, the simple devices are generally inadequate to provide accurate registered prosthetic restoration requiring frequent trips for adjustment while the complex devices are difficult to operate and require extensive training to use properly.
U.S. Pat. Nos. 4,734,033; 4,533,323; 4,449,930 and 4,382,787 disclose embodiments of a dental model articulators which comprise a pair of substantially U-shaped brackets having limbs which are pivotally interconnected through the use of snap-fit pivot fasteners.
In these embodiments, spherical members are formed integrally with cross-pieces of each of the U shaped brackets and a mounting member is provided for attachment to each cast. Each mounting member defines a socket in the rear portion within which the spherical member of one of the brackets fits to form a ball and socket joint.
A problem with this type of construction is that two adhesive bonds have to be formed for each cast; namely the bonding of the mounting member to the cast and the bonding of the spherical member in the socket. Furthermore, while the adhesive bonds are setting, the casts together with the articulator have to be held increasing a likelihood that the position of the articulator relative to the casts is moved during setting of the adhesive bonds. In addition with the provision of the snap fit type interconnection between the limbs of the brackets, lateral movement without the snap fit interconnections coming apart is limited.
U.S. Pat. No. 4,786,253 discloses a dental model articulator including two portions connected by a flexible hinge with ends of the portions having a socket and, spherical member for attachment in a semi-spherical cavity formed in the rear surface of the upper and lower teeth casts.
U.S. Pat. No. 4,797,097 discloses a dental articulator having a pair of attachment members, each of which is adapted to be mounted to a dental casting with a lockable ball joint attachment having one end formed with pins which are inserted into the cast. Likewise U.S. Pat. No. 3,916,524 discloses the use of pins which are inserted into bushing cast into the jaw molds. U.S. Pat. No. 4,319,875 shows a detachable fastener for joining impressions of a mouth onto a dental articulator using spherical members mounted in an articulator platform with the spherical portion of each member being mounted in a socket housing formed in the upper and lower jaw casts.
U.S. Pat. No. 4,207,677 discloses a dental model articulator with an upper jaw member and an intermediate connecting member having an over the center toggle type hinge and each jaw member being formed with a centrally disposed slot so as to leave a narrow passage or slit formed to receive a rib of the dental model mounting plate, thus facilitate positioning of the plate.
In addition various other hinged articulators of interest are shown by U.S. Pat. Nos. 4,439,151: 4,371,339: 4,263,715: 4,252,253: 3,510,947 and 2,697,279.